In the field of mammalian reproduction, many diagnostic procedures exist to aid the reproduction practitioner in making a diagnosis and choosing an appropriate course of action.
Currently, infertility in humans is defined as one year of unprotected coitus without conception. Approximately 10-15% of couples are affected by infertility. The risk of infertility is doubled for women between the ages of 35 to 44 as compared to women between the ages of 30 and 34. Approximately 600,000 couples sought professional help during the year 1968. However, in the early 1980's this number increased to over 2 million visits per year for infertility. Changes in fertility patterns will have a significant impact on the make-up of populations. It has been calculated that by the middle of the next century, the population in the United States will decline without immigration. Furthermore, the percent of people over the age of 65 will increase to over 23% in the next 100 years, resulting in an older and smaller work force.
In the United States, the majority of infertility can be accounted for by problems in the female. Evaluating a female for infertility can be complex. Examination of the fallopian tubes is an important early step in mammalian fertility evaluation due to the increased evidence of pelvic inflammatory disease. Currently, a hysterosalpingogram (HSG) is the procedure of choice to examine the patency of the fallopian tubes. In addition to HSG, hysteroscopy which is the direct examination of the uterus by a fiber optic device, is important to determine the presence of endometrial polyps, submucous leiomyomas, and other abnormalities within the uterus itself.
Another category of diagnostic procedures includes examination of ovarian function including ovulation and the secretion of progesterone during the luteal phase of the menstrual cycle. Ovarian function can be crudely assessed by measuring basal body temperatures during the menstrual cycle and cervical mucous testing around the time of ovulation. More accurate testing can be performed by measuring luteinizing hormone, a pituitary hormone which induces ovulation after a mid-cycle surge. Finally, serum progesterone levels can be measured to assess for normal luteal phase of the menstrual cycle.
The endometrium itself can be directly assessed by performing an endometrial biopsy three days before the suspected onset of menses. In assessing a mammalian endometrium, current gynecology and infertility physicians depend on pathologists to examine endometrial biopsies by hematoxylin and eosin staining of paraffin embedded specimens. For infertility patients, the reading of these biopsies provides information about the day of the cycle following ovulation, the adequacy of the luteal phase, and other potential data, such as infection, inflammation, or neoplasia of the endometrium. However, in most cases there is no evaluation of the functional and biochemical quality of the endometrium, and often no histologic reading to explain a patient's infertility problem.
Finally, the infertility patient could undergo endoscopic examination through an incision in the abdomen to directly visualize the external surfaces of the ovary, fallopian tubes and uterus to visualize any gross pathology which was not detected by previous examinations.
A high percentage of women who are unable to carry a pregnancy to full term undergo spontaneous abortion generally within the first six weeks. Pregnancy loss during the first six weeks has been shown to be as high as between 15 and 20%. Furthermore, the chance of a successful live birth after consecutive abortions without a live birth is only 40-50%.
Localization of trophoblast tissue, e.g., ectopic pregnancies and metastatic gestational trophoblastic disease are particularly challenging. The manifestations of tubal pregnancy are multiple. Amenorrhea, vaginal spotting or bleeding, abdominal or pelvic pain, presence of a pelvic mass and an increased body temperature may be present in a variety of combinations in the presence of ectopic pregnancy. Laboratory testing for suspected ectopic pregnancy includes hemoglobin and hematocrit, white blood cell count, urine and serum .beta.-HCG pregnancy test, ultrasound including vaginal probe ultrasound, culdocentesis (a diagnostic procedure to detect blood in the peritoneum), curettage of the endometrium to rule out the presence of products of conception within the uterus, laparoscopy and finally in emergency cases, laparotomy. Given the wide variability of patient presentation and the course of ectopic pregnancy, the accurate diagnosis of this disorder is the most difficult one to make in obstetrics and gynecology. In one study of three hundred women, approximately a third were seen more than once, and 11% were seen more than twice before the correct diagnosis was made. In addition, in a recent study of deaths from ectopic pregnancy, more than half of the cases were misdiagnosed leading to fatal maternal outcome. Clearly, accurate and rapid diagnosis and treatment of an ectopic pregnancy would be an important advance for the field of obstetrics and gynecology.
The current modalities for detecting metastatic gestational trophoblastic disease include serum hCG level determination, chest x-ray, pelvic ultrasound, CT scan of the abdomen pelvis and head. Like in other solid tumors, small metastases can be missed by these procedures. The knowledge of the presence of metastases is critical for the successful treatment of this and other tumors. Therefore, a method which can localize and detect small quantities of trophoblast would be very helpful for the treatment of this disease.
A teratogen is any agent which induces alteration in form or function of a fetus when administered during pregnancy. In considering the effects of drugs during pregnancy, gestation is generally divided into three periods: (1) the ovum and fertilization to implantation; (2) the embryonic period from the second to the eighth week; and (3) the fetal period, from after eight completed weeks until term.
Given the wide variety of drugs available as well as many complex factors during gestation, it has been concluded by many people in the field of mammalian reproduction that there is a severe lack of information regarding the majority of drugs, and the potential detrimental effects of these drugs during pregnancy. The Food and Drug Administration in 1979 established five categories for medications with regard to possible adverse fetal effects. Category A includes drugs which in controlled studies in humans have demonstrated no fetal risk. There are very few drugs in this category and they include multi-vitamins and pre-natal vitamins. Category B are drugs in which animal or human studies have not demonstrated a significant risk. These drugs have been shown to have no animal fetal risk but no evidence is available in humans. Penicillins fall into this category. Category C are drugs in which no adequate studies in either animals or humans have been performed. Many drugs taken during pregnancy fall into this category. Category D are drugs in which there is evidence of fetal risk but certain clinical benefits outweigh the risks. An example are the anti-convulsants. Category X are drugs with proven fetal risk which are not outweighed by any benefits.
Contragestion, or post-coital contraception is currently practiced by two basic methods: surgical and medical. In the 1970's the "morning after pill" (diethylstilbestrol) was popular as a post-coital contraceptive method. More recently, the use of the anti-progesterone RU-486 has gained wide acceptance in Europe to terminate pregnancy soon after fertilization and implantation. During the first trimester, the most common technique to end a pregnancy is by surgical abortion. Surgical abortions generally involve cervical dilation and curettage or vacuum aspiration. Finally, after the first trimester, labor inducing medications such as oxytocin and prostaglandins can be utilized to induce premature delivery and thus the termination of pregnancy. The medical techniques described above are known to have a number of adverse reactions and potential complications. The surgical technique can lead to uterine rupture, hemorrhage, and infection.
In the United States, the commonly employed contraceptive techniques include oral steroidal contraceptives, injected or implanted steroidal contraceptives, intra-uterine devices, physical, chemical, or physicochemical barrier techniques, withdrawal, sexual abstinence around the time of ovulation, breast feeding, and permanent sterilization. In addition to the high failure rates of some of these methods, a number of these methods have serious potential complications for the users. For example, in addition to metabolic changes induced by oral contraceptives, there is possibly an increased risk of neoplasia, nutritional disorders, cardiovascular effects, thromboembolism and even death.
In vitro fertilization (IVF) requires the removal of ova from a mammalian ovary, and exposure of these ova to sperm outside the body. Fertilization of each ovum requires that at least one living sperm penetrates the zona pellucida (outer covering) of the ovum and fuses with the pronucleus. Once this has occurred and the ova are fertilized, they can be transferred to a uterus where they can become implanted on the uterine wall. If implantation occurs, the pregnancy can proceed as if fertilization had occurred within the body. In vitro fertilization has gained widespread professional and public acceptance. However, despite the ever increasing frequency and refinement of this procedure, in vitro fertilization attempts most often do not result in pregnancy. In vitro pregnancy rates are currently only about 15 to 20 percent. For a variety of reasons, exposing the ova to sperm does not necessarily result in fertilization. Furthermore, even where the ova is fertilized, the placement of the ova in a uterus usually does not result in normal implantation. The low success rate of IVF often leads to an excessive financial and psychological burden for the infertile couple.
Other assisted reproductive technologies include two modifications of the IVF technique. The first is gamete intra-fallopian transfer (GIFT), the second is zygote intra-fallopian transfer (ZIFT). In the GIFT procedure, the retrieved oocyte and sperm are mixed together and placed back into the fallopian tube where fertilization takes place. The fertilized zygote then travels down through the fallopian tube into the endometrial cavity, where implantation may or may not take place. The ZIFT procedure allows for fertilization to take place in vitro as in standard IVF, and then the fertilized zygote is placed back in the fallopian tube where it then travels down into the uterus to implant. Finally, it is becoming realized that the hyper-stimulation protocols necessary to retrieve many oocytes from the donor woman may have deleterious effects on the endometrium itself and decrease the rates of implantation. Two basic procedures have been utilized to help overcome this problem. The first is considered non-stimulated oocyte retrieval. A single egg is retrieved, allowed to be fertilized and placed back into the fallopian tube or uterus for implantation. The other technique involves the hyper-stimulation portion of the IVF procedure to retrieve the eggs and allow for fertilization in vitro. The zygotes are then frozen to be placed back into the patient after several normal cycles, with the hope that the endometrium will be more receptive to implantation. All of these techniques attempt to maximize the quality of the eggs, zygotes produced after fertilization and the receptivity of the endometrium. Any procedure which would enhance the implantation rate above the standard 15 to 20% would have a marked positive effect on any of these technologies.
Notwithstanding the work reported in this field, a need still exists for improved diagnostic and therapeutic applications in the field of mammalian reproduction.